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Morning sickness

Morning sickness, also called nausea and vomiting of pregnancy (NVP), is a symptom of pregnancy that involves nausea or vomiting.[1] Despite the name, nausea or vomiting can occur at any time during the day.[2] Typically these symptoms occur between the 4th and 16th week of pregnancy.[2] About 10% of women still have symptoms after the 20th week of pregnancy.[2] A severe form of the condition is known as hyperemesis gravidarum and results in weight loss.[1][6]

Morning sickness affects about 70-80% of all pregnant women to some extent.[4][5] About 60% of women have vomiting.[2] Hyperemesis gravidarum occurs in about 1.6% of pregnancies.[1] Morning sickness can negatively affect quality of life, result in decreased ability to work while pregnant, and result in health care expenses.[3] Generally mild to moderate cases have no effect on the baby.[1] Most severe cases also have normal outcomes.[1] Some women choose to have an abortion due to the severity of symptoms.[1] Complications such as Wernicke encephalopathy or esophageal rupture may occur but are very rare.[1]

An increase in human chorionic gonadotropin. It is probably not the HCG itself that causes the nausea. More likely, it is the HCG stimulating the maternal ovaries to secrete estrogen, which in turn causes the nausea.[11]

Morning sickness may be an evolved trait that protects the baby against toxins ingested by the mother. Evidence in support of this theory includes:[12][13]

Morning sickness is very common among pregnant women, which argues in favor of its being a functional adaptation and against the idea that it is a pathology.

Fetal vulnerability to toxins peaks at around 3 months, which is also the time of peak susceptibility to morning sickness.

There is a good correlation between toxin concentrations in foods, and the tastes and odors that cause revulsion.

Women who have no morning sickness are more likely to miscarry.[14] This may be because such women are more likely to ingest substances that are harmful to the fetus.[15]

In addition to protecting the fetus, morning sickness may also protect the mother. A pregnant woman's immune system is suppressed during pregnancy, presumably to reduce the chances of rejecting tissues of her own offspring.[16] Because of this, animal products containing parasites and harmful bacteria can be especially dangerous to pregnant women. There is evidence that morning sickness is often triggered by animal products including meat and fish.[17]

If morning sickness is a defense mechanism against the ingestion of toxins, the prescribing of anti-nausea medication to pregnant women may have the undesired side effect of causing birth defects or miscarriages by encouraging harmful dietary choices.[12]

^Thomson, M.; Corbin, R.; Leung, L. (2014). "Effects of Ginger for Nausea and Vomiting in Early Pregnancy: A Meta-Analysis". The Journal of the American Board of Family Medicine. 27 (1): 115–122. doi:10.3122/jabfm.2014.01.130167. ISSN1557-2625.

^Tiran, Denise (Feb 2012). "Ginger to reduce nausea and vomiting during pregnancy: Evidence of effectiveness is not the same as proof of safety". Complementary Therapies in Clinical Practice. 18 (1): 22–25. doi:10.1016/j.ctcp.2011.08.007. ISSN1744-3881.